A missing piece of DNA causes some grey squirrels to have black fur, according to new research.

The investigation, led by by Helen McRobie of Anglia Ruskin University (ARU), found grey squirrels inherit a normal pigment gene from both parents, while black squirrels inherit a gene with a missing piece from both.

Ms McRobie, a senior lecturer in biomedical scence, said: “If you look closely at grey squirrel hairs, they are not actually grey at all but are a combination of white, black and orange stripes.

“Our research shows that one hormone turns the switch on to make black fur, and a different hormone turns the switch off to make orange and white fur. So in the grey squirrel, as the fur is growing, the switch turns on and off to make the stripes.